Diffusion-Weighted Imaging of the Rat Hippocampus with Mild Traumatic Brain Injury

Place an anesthetized rat with a mild traumatic brain injury (mTBI) on the magnetic resonance imaging (MRI) scanner bed in a prone position.

Position the radiofrequency coil over its head to ensure optimal signal-to-noise ratio.

Advance the scanner bed into the scanner bore and perform a three-plane scout scan to center the brain within the magnetic field.

Acquire T2-weighted images to check for abnormalities. Then, position the slice package to include the brain bulb and cerebellum.

Next, load the diffusion-weighted imaging sequence and configure diffusion parameters to capture microstructural details.

Restrict the field of view to the cerebrum to minimize artifacts and reduce scan time.

Acquire diffusion-weighted images (DWI) sequentially to measure water molecule movement within brain tissues.

Bright areas on DWI indicate restricted diffusion, highlighting axonal injury and hippocampal microstructural damage from mTBI.

After completion of the scan, allow the rat to recover.

Before, and one day following the trauma induction, confirm a lack of response to toe pinch in the experimental animal, and place the animal on the MRI scanner bed in a head-first prone position. Slide the quadrature volume coil over the head, and advance the scanner bed into the scanner bore. To ensure a correct positioning, obtain a default three-plane scout scan. When the scan is finished, load the scan in the image display and ensure that the head is lying straight, and that the brain is positioned in the center of the magnet and coil.

Acquire T2 weighted images using the default settings, except for the field of view and matrix size, which should be adjusted to a higher in-plane resolution of 109/109 micrometers. Open the geometry editor and place the slice package in the correct position, including the bulbous of the brain and the cerebellum. And load three new echo planar diffusion-weighted spin echo sequences from the B_ diffusion folder into the scan control protocol.

Acquire diffusion-weighted images using the default settings and open the Edit Scan tab. Set the slice orientation to Axial, and the number of slices to 25, to achieve a slice thickness of 500 micrometers, and an inner slice distance of 600 micrometers, and amend the readout direction into left right. Under the Geometry tab, adjust the geometrical parameters, and adjust the field of view and matrix size to 105 by 105 to ensure a resolution of 333 by 333 micrometers.

Click the diffusion tab within the Research tab for each of the three diffusion shells, and adjust the number of diffusion directions to 32 for the first shell, 46 for the second shell, and 64 for the third shell. Change the number of B0 images to 5 for the first shell, 5 for the second shell, and 7 for the third shell. And adjust the gradient directions with custom gradient direction files.

Adjust the B value per direction to 800 seconds per millimeter squared for the first shell, 1,500 seconds per millimeter squared for the second shell, and 2000 seconds per millimeter squared for the third shell. Then open the geometry editor and place the field of view between the bulbus and cerebellum, containing only the cerebrum to reduce the artifact and scan time.

At the completion of the scanning protocol, transfer the animal from the scanner bed to a clean cage with a 37 degree Celsius heating pad, with monitoring until full recumbency.